Receiving apparatus



Patented July 12, 1921.

,..VWQNIKTED STATES PATENTv OFFICE.-

SIDNEY omnia@ nimoWN, oF NORTH Aaron, ENGLAND.

TELEPHUNE :anonime ArrAmi'rns.

Application led October 9, 1924; Serial No. 742,716, and in Great Britain( November 30, i923.

This invention relates to telephone receiving apparatus in general 'and more pa'rticw lai-ly for use in connection'with 'Wireless telegrapliy or telephony.

The object ot the presontrinvention is to amplify week electrical currents such as are derived for instance from a crystal detector to such an extent` that they will operate a loud speaker; more particularly, the invention has for its object the provision of a unitary mounting in which the microphone amplitier is insulated from the telephone receiver so that mechanical vibration produced by the lutter cannot be transmitted through the lmounting to the ainplilier toallect the operation of the microphone.

With suoli object, the invent-ion consists in the improved apparatus for transmitting or reproducing sound hereinafter described und more par icularly pointed` out in the claims.

In order that the said invention may he clearly understood and readily carried into effect, one lorin will now be described by Way of example with reference tothe accom panying drawings, in WhichzM .Figure i is u 'vertical section of the com plete instrument; y

Figure 2 is a plan with the sound horn and the cover or casino; of the amplifier removed and. showing the diierentinl 1nicrophone in section, and

Figure 3 is a diagram of the connections.

A metal hase, A, is providedwhich carries both the ainplilier anni the telephone rcceiver, the latter heine" enclosed in :i easing', a, which orins :in integral part ot' thc brise, A, und is raised, :trom the hase on the legs, o. The easing, a, has fit its upper side n cent'i'il hollow boss, a?, which receives the snmller end of the sound horn or trumpet,y

l, which is ot any ordinariv torni, irre easing a. is open at; its under sido und the onse -platte has :i coincident opening` nnineclizztrly helen' to pcrniit the insertion of- -so :is to project itt :in :i

Thisis secured around its edge to the onder side of the flanged. rim, of", oy ineens of the stitfening plates, c, and set screws, c, the plates firmly clamping the rubber support,

,CQ to the flanged rim, a3.

`On the upper side of the support or met, C, is Jfirmly secured the stout bracket, D., which carries the microphone aunpiilier, the flange, (l, of the bracket being' clamped upon the support, C, hy the set screw, ci", find. the clamping plate, c2, piaceri below ne snp port, C, the plato7` c, giving the nests rigidity to the centre oi? the rubber snp The amplifier magnet., E, is inountetl on tiie'upright foce olf the bracket', D, in iin adjustable manner by the holte, E, liv, the holt, l?, being screwed into the brochet, l), and clamped to the two legs of the magnet, which is of horseshoe forro, towards theirs/ole end. hy the clun'iping plates, f. und nuts, f', while the holt., it", which placed townrcls the other end of the magnet, is provided with aispiing, f2, piaceri hei-Ween the iii-octet, l), and one of the clamping plates, so to pressthe round end of: the magnet ref silicntly away from the bracket. The .nionnting oi the holt', l?, is ntljf/ yieldH nig to permit a small angular adjustment oit the, magnet: according to the setting' of the holt, Ff, which is provided :it its onter ond ivit-h an, adjusting screw, (l, which allows :i lnnited 'turning movement, the :screw slight ly lengthening or shortening the etl'eciire length of they holt, F, so that the @wie enti oi the magnet may he Mijn t l i I position with great' through zt very silo-ull distance accuracy.

A llfiie pole end of the magnet carries the polo pieces, j, which are inou noon :1. clnnn'l'ererl portion on the. erfhv .lie of about. `45',

these pole pir-res cnr :ying t te .motivine` coils, inenioors, 7"5, ie still steel remi. I, towards Il', and 'terni sting; in po 'placed closely adinet-nt to tl tl. which rigidly inonnteti :it one 'enti on the 'lace oi the hrzrcl reducer. end, i, of the reed is i. neetetl through the rod, to central 'plate or electrode, Z2', of the, ditierentiril l), The

inierophonerl, which olf known type the plate. fr". lying between two layers of coihon granules in the Cell, olf the inicropiione casino, the granules tilting the. spaces hcrrveen th central plate and the und plates, icl?, It", which :ire usually of carbon, The

nity eonool ilfil:

plates are, of course, insulated from one another excepting through the carbon grannies.

The telephone receiver', L. is of the Well known Brown loud speaker type, comprising av iightconical diaphragm, Z, mounted on the end oit the steel reed, Z', which is vibrated by the receiving elcctromagnet, Z2, the poles of which are close to the reed. The us el adjustments are provided and es the felice is a lrnownone there is no need to describe it in detail. The centre of the conica-l diaphragm lies immediately below the hollow boss, a, receivingl the end of the sound horn, B, so that the sound vibrations emitted by the diaphragm, Z, pass through the expanding horn.

The only material distinction between the telephone receiver, L, as employed in this device and as hitherto used lies in the Windings, lli, of the elcctromagnet, Z2, and the circuits are shown in Figure 3 Where the Windings, M, of the. receiver magnet are shown as two pairs of coils which are Wound differentially. For convenience the base, A, is employed part of the circuit and the coils, lli, are connected to the base in the manner indicated, the connection being?, carried from opposite ends ot the tivol pairs of coils, While the other ends are connected, respectively, to 'the trvo outer plates, fc3 and flot, of the microphone. Ylfhe positive terminal, N, oi the source of current supplied to the microphone is also connected to the frame, A, While the negative pole, N', is connected te the centre plate, c, of the microphone. The reed, J, ot the relay is indicated as attached to the plate, Zz. and the coils, H, of the electromagnet E, are connected to the terminals, 71 to which are attached the connections from the source ot weak electric-.rl currents to be mainitled, such as those furnished by a crystal detector used in Wireless telegraphy or telephony.

it will be seen that any oscillation of the reed, J, duc to the Weak currents passing through the amplifier receiving: coils` H, causes the centre plate, v, of the microphone to vibrate and rary the cnrrentin opposite directions between the centre pla/te and the two outer plates. 7c3 and le". with the rer-ult that the greatly magnified currents in the microphone circuit cause correspondingly increased ell'ects on the reed. Z, oi the telephone receiver, L.

rlhe source ot current connected to the terminals. N', may be. in the form of a battery ot about tl volts, a very small cnrrent being' required as the resistance of the mi.' oplionc and the telephone. windings is cons lgable. The amplifier is, therefore, suitable for use with dry cells as the source of the microphone current.

The complete microphone amplifier is enclosed in the detachable cover or case, O

mounted upon the rim,l a3, of the base, A, and secured by bayonet Joint or other simple connections. On the` top of this case and independent of any connection with the afmpliiier is the magnetic adjuster, P, in the form of a knob mounted to turn freely around the stein, 77, which is secured in the top ofthe case and carrying the small perinanent magnet, 79', Which consists of a simple straight rod highly magnetized and passing transversely through the knob, P, at a. short distance from the axis. The magnet, p', is situated over the ampliiiermagnet, E, and on turning the knob it can take up any angular position relatively to the magnet, E. It is found that the amplification obtainable can be greatly increased by suitably adjustin the knob, P, the eect ofthe magnetic eld due to the small magnet, p', greatly influencing the action of the ampliiier magnet on the reed, J. The knob is, therefore, turned by the listener during the reception of sound until the sound is at a maximum, or if it is too loud the magnetic adjuster can be turned to reduce it to any required degree.

Having now described my invention, what I claim as nenT and desire to secure by Letters Patent is l. A mounting for loud speaker apparatus comprising a, base plate having an opening in one end thereof, a telephone receiver mounted on the other end of said plate, a. sound insulating mat secured to the base plate Within said opening, a cover seated on the base plate over the sound insulating mat to provide, a closed chamber, and a microphone amplifier mounted in said chamber on the mat and having electrical connections with the telephone receiver and also electrical connections leading to the exterior of the chamber to contact terminals for the circuit of the Weak current that is to be amplified.

2. A mountingr for loud speaker apparatus comprising,r a. base plate having an opening in one end thereof, a casing on the other end closed at its top except for a sound outlet, a telephone receiver mounted in said casing, a sound. insulating mat clamped to the base plate Within said opening, a cover removably seated on the base plate over the insulating rhat to form a. closed chamber, a bracket within said chamber secured on said mat. and a microphone amplifier mounted on the bracket Within the chamber and hav.- ing electrical connections with the telephone receiver and also connections leading;r to the exterior ot the chamber tc Contact terminals for the circuit oif the vrealr current that is to be amplified.

A mounting "for loud speaker apparatus comprising a base plate having,l openings in its opposite ends, a cylindrical casing on one end of the base plate over the opening therein and having an open bottom opposite to the opening inthe adjacent end of the base Closed top having 'Ell hollow boss projeting tl'ierefrom to provide a sound outlet, a te1e- Ebene receiver in said casing, said base plate aving a anged rim at the opening in its other end, va sound insulating matremovably attached in the inner side of the Hanged rim, a cover detaehably seated on the base 'plate around said rim and over `seid mat to pron vide e closed chamber, a bracket removably1 clamped on the 112343,v and a, lnierophene :irre

pier carried by said bracket within said chamber and having relectrical connections eading to the exterior of the chamber to Contact :erminals for the circuit of the weak current that is to he amplified, said amplifier aise having eectrieai connections with the teiephone receiver. V

En testimony' whereof I have signed my name to this specification.

Smm-Y GEORGE BROWN. 

